1. Technical Field
The disclosure relates to a signal processing method, and more particularly, to a signal processing method for use in a touch panel.
2. Description of the Prior Art
Flat panel displays (FPDs) have advantages of a thin profile, low power consumption, and low radiation, and are broadly adopted for application in a variety of electronic appliances such as media players, mobile phones, personal digital assistants (PDAs), and computer monitors, etc. Besides, along with the requirement of a friendly communication interface for a user to interact with an electronic device, a touch-sensitive display device for controlling operations of the electronic device, instead of using a keyboard or a mouse, has steadily become the mainstream.
In general, the touch-sensitive display device may employ a resistive touch panel or a capacitive touch panel to sense touch input. The resistive touch panel locates touch input positions through voltage drops, but is unable to provide multitouch input functionality. The capacitive touch panel typically includes sensing capacitors, and performs signal processing on capacitance variations of the sensing capacitors corresponding to touch points for locating touch input positions, which is able to provide multitouch input functionality, thereby gaining increasing popularity.
In view of that, the flat panel display having touch sensing mechanism normally includes a display panel and a capacitive touch panel attached thereon. The operation of the capacitive touch panel may be performed based on a sensing judge array 100 illustrated in FIG. 1 so as to provide a means of ascertaining the occurrence of a touch event corresponding to the sensing judge array 100. As shown in FIG. 1, the sensing judge array 100 is a 3×3 array having a first touch sensing unit SUc and a plurality of second touch sensing units SUa1˜SUa8 adjacent to the first touch sensing unit SUc. The first touch sensing unit SUc is employed to output a first sensing signal SSc, and the second touch sensing units SUa1˜SUa8 are employed to output plural second sensing signals SSa1˜SSa8 respectively. A signal processing method applied to the sensing judge array 100 may comprise calculating an average of the second sensing signals SSa1˜SSa8, summing up the average and a preset first threshold value for generating a second threshold value, and comparing the first sensing signal SSc with the second threshold value for judging whether a touch event is occurring to the first touch sensing unit SUc.
However, the aforementioned operation of calculating the average of the second sensing signals SSa1˜SSa8 tends to incur a reduction of signal processing accuracy. Besides, while the display panel is performing an image data writing operation, the sensing operation of the capacitive touch panel may be seriously interfered by noise-like electric field generated in the polarity alternating process of writing high-voltage pixel signals, which may cause the capacitive touch panel to output error sensing signals. In particular, as a heavy touch event is occurring to the capacitive touch panel, the interference of noise-like electric field within a heavy touch influencing area becomes much more serious, such that the operation of the signal processing method is more likely to misjudge touch events over error sensing signals, thereby resulting in malfunction of backend circuit. Finally, if the first threshold value is increased for avoiding an occurrence of misjudging touch events, the operation of the signal processing method may be unable to detect a soft touch event.